Showing papers on "Ettringite published in 1985"
TL;DR: In this article, the aggregate-mortar interface is studied by scanning electron microscope and X-ray diffraction and it is confirmed that calcium hydroxide and ettringite are formed by a "through-solution" mechanism in this zone.
118 citations
TL;DR: The mechanisms of zinc and mercury leaching from cement/silicate stabilization processes have been assessed from extended leaching tests, scanning electron microscopy and powder X-ray diffraction.
66 citations
TL;DR: In this paper, a quantitative Xray diffraction technique was used to determine the amounts of thaumasite, ettringite and gypsum present in a mortar sample, and it was shown that if conditions are favourable then thaumase formation can proceed rapidly and can even result in the complete breakdown of very strong renders.
58 citations
51 citations
TL;DR: The stability of the ettringite phase in relation to its solubility in pure water has been studied at 30°, 60° and 100° for a time interval of 14 days.
36 citations
TL;DR: In this paper, a method for quantitative Xray diffraction analysis (QXDA) of three sulphate minerals frequently associated with building materials has been devised, including ettringite, thaumasite, and gypsum.
34 citations
TL;DR: In this article, the hydrogen NMR parameters T 1, T 2 and M oi of a white cement were monitored as a function of hydration time, from the nature and time evolution of the same 20 observables that eventually developed, a partial description of the dynamics of cement hydration was proposed.
34 citations
TL;DR: In this paper, a thermogravimetric method is described by which the stability of ettringite may be evaluated, and a synthetic hydrate was prepared and its composition verified by XRD, SEM and thermograves.
15 citations
TL;DR: The influence of 0.3 wt% gluconute, lignosulfonate, or glucose on the hydration of 4CaO·A12O3-Fe2O3 in the presence of gypsum with or without Ca(OH)2, was examined in this article.
Abstract: The influence of 0.3 wt% gluconute, lignosulfonate, or glucose on the hydration of 4CaO·A12O3-Fe2O3 in the presence of gypsum with or without Ca(OH)2, was examined. In the absence of Ca(OH)2 all the admixtures retard both ettringite production and subsequent conversion of ettringite into the monosulfate in the decreasing order glucose >lignosulfonate >gluconate. In the presence ofCa(OH)2 all the admixtures accelerate early ettringite production but do not affect subsequent conversion of ettringite into the monosulfate, at least up to 28 d.
14 citations
TL;DR: In this article, the hydration characteristics of metakaolin and gypsum mixtures were studied by the determination of their hydration products using XRD as well as DTA techniques, and the effect of the phase constituents on the compressive strength of the hardened pastes was also investigated.
10 citations
01 Aug 1985
TL;DR: In this paper, a study of the temperature stability of ettringite and chloroaluminate in a hydraulic-cement system for underground isolation of nuclear wastes is presented.
Abstract: : As part of the study of hydraulic-cement system for use in possible underground isolation of nuclear wastes, this study was made to determine the temperature stability of ettringite and chloroaluminate. Either or both of these phases may be expected in a hydraulic cement system depending on the presence of salt. (NaCl). The study of ettringite was made using 15 mixtures that contained portland cement, plaster, 2 levels of water, and in some mixtures, 1 of 6 pozzolans (3 fly ashes, 1 slag, a silica fume, a natural pozzolan), plus a 16th mixture with anhydrous sodium sulfate replacing plaster (CaSO4 . 1/2H20). Specimens were made and stored at 23, 50, and 75 C or 23, 75, and 100 C (all four temperatures in one case) for periodic examination by x-ray diffraction for phase compositiion and ettringite stability, and testing for compressive strength and restrained expansion. A more limited study of the stability of chloroaluminate was made along the same lines using fewer mixtures, salt instead of plaster, and higher temperatures plus some pressure. It was found that while some ettringette was decomposed at 75 C, depending on the composition of the mixture, all ettringite was undetectable by X-ray diffraction at 100 C, usually within a few days. The evidence indicates that the ettringite became amorphous and no significant test phases formed in its place. Since there was no corresponding loss in strength or reduction in volume, this loss of ettringite crystallinity was considered to be damaging. Based on much more limited data, chloroaluminate was found to decompose between 130 C at 25 psi and 170 C at 100 psi; no significant phases replaced it.
TL;DR: The formation of ettringite (C6AS−·32H) in diluted water suspensions was studied in this paper, where the solid components were taken in mole rations 1:8:6 (C4A3S−, CS−H2 and CS respectively).
TL;DR: In this paper, the authors used physico-chemical experiments to determine the cementitious components of this fly ash through its dissolution in pure water and in lime water, and showed that after 7 days, mortar cubes made with fly ash showed a slight compressive strength increase when compared to a reference mix containing the same amount of quartz.
Abstract: A silico-aluminous (Class F) French fly ash has been studied during the last ten years. While over this period the fly ash was produced from different bituminous coals, it has demonstrated high constancy in terms of its chemical and physical composition as well as cementitious properties. The first part of this paper gives a complete physico-chemical characterization of this fly ash, including chemical composition, mineralogical composition of its crystallized fraction, chemical composition of its glass, grain-size distribution, specific surface area, and bulk density. The second part deals with physico-chemical experiments performed to determine the cementitious components of this fly ash through its dissolution in pure water and in lime water. The lime water experiment was also carried out on a washed sample containing few residual sulfates. This series of experiments demonstrates the importance of sulfates in this particular fly ash, especially during the early stages of hydration. Their action results in the formation of ettringite. The cementitious role of these sulfates has been confirmed by comparing the compressive strength of mortar cubes containing washed and nonwashed fly ash. After 7 days, mortar cubes made with this fly ash showed a slight compressive strength increase when compared to a reference mix containing the same amount of quartz. This compressive strength increase can be related to the formation of C-S-H due to the pozzolanic reaction. After 8 months, the pozzolanic reaction had consumed most of the lime generated by the hydration of C 2 S and C 3 S, so that practically no portlandite remained in the mortar.
TL;DR: In this article, reaction products of high lime fly ash (FA), mixed with distilled water and hydrated in contact with Portland cement (PC), and in hardened PC/FA pastes of various mix proportions, were examined by SEM and EDX.
Abstract: Reaction products of high lime fly ash (FA), mixed with distilled water and hydrated in contact with Portland cement (PC), and in hardened PC/FA pastes of various mix proportions, were examined by SEM and EDX. Structures contributing to early strength originated mainly through solution depositions of ettringite, and portlandite. Some evidence of ettringite instability suggested gypsum deficiency in PC/FA mixtures.
01 May 1985
TL;DR: In this article, the effect of lime on the hydration of tricalcium aluminate in presence of gypsum has been studied at 30 degree by means of X-ray powder diffraction as well as the chemical methods of analysis.
Abstract: The effect of lime on the hydration of the tricalcium aluminate in presence of gypsum has been studied at 30 degree by means of X-ray powder diffraction as well as the chemical methods of analysis. The behavior of the reactants and products has been related to the solution composition for a reaction time of two minutes to one week. Lime depresses the concentration of aluminum in solution completely, retards the increase in the ettringite formation which is accompanied by a decrease in the sulfate ion concentration in the bulk solution and delays the consumption of both gypsum and C//3A.
Patent•
05 Oct 1985
TL;DR: In this article, the water absorbing and deodorizing action of ettringite acts and environmental enhancement can be achieved by using a particulate material containing dehydrated ettricite as an effective component.
Abstract: PURPOSE:To keep a clean state, by using a particulate material containing dehydrated ettringite as an effective component. CONSTITUTION:Ettringite represented by C3A.3CaSO4.32H2O is heated at 200 deg.C or more to obtain a dehydrated substance. Said dehydrated ettringite is mixed with straw or dust. By this method, the water absorbing and deodorizing action of ettringite acts and environmental enhancement can be achieved.
Patent•
06 Sep 1985
TL;DR: In this article, a grout consisting of a slurry of mixed powder of fine particles of alkali rock, lime and cement-based solidifying auxiliary is used to solidify soft ground readily and almost permanently.
Abstract: PURPOSE:To solidify soft ground readily and almost permanently, by pouring into the ground a grout consisting of a slurry of mixed powder of fine particles of alkali rock, lime and cement-based solidifying auxiliary. CONSTITUTION:A cement-based mixed powder which has tackiness and self-curing property and in which ettringite has been formed, is prepd. by adding 30- 5pts.wt. cement-based solidifying auxiliary to 70-95pts.wt. mixt. of about 70- 90wt% fine particles of montmorillonite-contg. alkali rock having a particle diameter of about 0.074mm. or smaller and 30-10wt% quick lime and/or slaked lime. Sea water or rock salt water is added to the mixed powder and the resultant slurry is poured into ground.
Patent•
16 Aug 1985
TL;DR: In this article, a material contg ettringite dehydrated by heating is admixed with sludge such as industrial wastes, urban wastes, weak soil, etc contg a large amt of water to dehydrate and solidify the sludge.
Abstract: PURPOSE:To facilitate transportation, dumping, or reclamation, etc of industrial wastes, urban wastes, weak soil, etc contg large amt of water, or other hydrous sludge by mixing a material contg ettringite dehydrated by heating with hydrous sludge CONSTITUTION:A material contg ettringite dehydrated by heating is admixed with sludge such as industrial wastes, urban wastes, weak soil, etc contg a large amt of water to dehydrate and solidify the sludge For example, hydrated ettringite is calcined at 900 degC for 1hr 75% said calcined ettringite basing on the sludge having 200 water/solid ratio (W/S) is added to the sludge and mixed by stirring The sludge is coagulated after 35min to form dry and crumbly earthy material, which is odorless, and no abnormality is noted even after 3 years from reclamation
Journal Article•
TL;DR: The effect of calcium lignosulfonate (CLS) on the early hydration characteristics for clinker minerals was investigated in this paper, where the hydration of C₃A lowered CLS adsorption to form ettringite and the residual CLS in the liquid phase accelerated the solubility of c₄AF hydration.
Abstract: The effect of calcium lignosulfonate (CLS) on the early hydration characteristics for clinker minerals was investigated. In the presence of CLS and unsufficient gypsum, The hydration of C₃A lowered CLS adsorption to form ettringite and the residual CLS in the liquid phase accelerated the solubility of C₄AF hydration. As the result, unreacted Fe 3+ in the liquid phase would be precipitated gelatinously on C₃S hydrates and the hydration of C₃S could be retarded. But by addition of optimum gypsum into the cement with CLS, the presence of Fe 3+ in the liquid phase were lowered and C₃S hydration would be normallized.